Leaving the middle seats blocked on planes could reduce exposure of the new coronavirus by as much as 57%, according to a new study released by CDC on Wednesday.
For the study, researchers from CDC and Kansas State University (KSU) used data from a KSU study in 2017 in which researchers sprayed an aerosolized virus through two mock airplane cabins: a single-aisle plane and a double-aisle, wide-bodied plane. The researchers then modeled how a virus would spread if every middle seat was open in a 20-row single-aisle plane.
They found that blocking the middle seat reduced the risk of coronavirus exposure anywhere from 23% to 57% compared with a full flight. That reduction in risk resulted from two factors, the researchers said: increased distance between infectious passengers and other passengers, and a decrease in the total number of people in an airplane, which reduces the odds an infectious passenger would be on board.
However, the researchers cautioned that the study "addresses only exposure and not transmission."
In addition, they said the study did not take into account mask-wearing—which is currently required on all flights—"because masks are more effective at reducing fomite and droplet exposures than aerosol exposures."
CDC Public Affairs Specialist Jade Fulce said of the findings, "Physical distancing of aircraft passengers, including through policies such as middle seat vacancy, could provide additional reductions in SARS-CoV-2 exposure risk." She added, "Some airline carriers have been operating with a vacant seat policy, and this study supports the effectiveness of that intervention, in the context of other measures that are in place."
However, not taking mask-wearing into account may overestimate the benefit of middle-seat blocking, Joseph Allen, a ventilation expert at the Harvard T.H. Chan School of Public Health, said. "In general, I would think that wearing a mask would make this effect much less pronounced," he said, adding that exposure to the virus doesn't necessarily mean someone will be infected by it.
"I'm surprised to see this analysis come out now, making a big statement that middle seats should stay open as a risk-reduction approach, when the model didn't include the impact of masking," Allen said. "We know that masking is the single most effective measure at reducing emissions of respiratory aerosols."
As interest in travel picks back up, most experts voiced doubt that the study would result in airlines suspending the sale of middle seats. While airlines did suspend the sale of middle seats earlier in the epidemic, nearly all have since reinstated it. The last holdout among major airlines, Delta Airlines, is scheduled to drop its ban on May 1, in large part because of the anticipated growth in vaccination rates.
"This is a giant bombshell from the CDC," Henry Harteveldt, an industry analyst and co-founder of Atmosphere Research Group, said. "I think the airlines are going to look at it and say, 'That's nice. We're not going back to blocking middle seats.'"
Similarly, Scott Keyes, founder of Scott's Cheap Flights, said airlines were able to block middle seats last year because flights were generally only 30% full as a result of decreased demand. Now, airlines are seeing at least 75% capacity on average, Keyes said, and blocking middle seats would cost airlines millions of dollars.
"With vaccinations accelerating and travel interest rebounding sharply, it's more likely that President Biden will dunk a basketball on live TV than airlines will reimpose middle-seat blocking," Keyes said (Dietrich et. al., Morbidity and Mortality Weekly Report, 4/14; Compton, Washington Post, 4/14; Chander, Reuters, 4/14; Anthes, New York Times, 4/14; Levin/Schlangenstein, Bloomberg, 4/14).
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